This invention relates to endothelin converting enzymes of mammalian cell origin or mammalian blood origin having the activity of converting big endothelin to endothelin, and a process for preparing the enzymes from mammal cells or mammal blood by extraction and purification.
Endothelin is an endothelial cell-derived vasocontrictor peptide discovered by Yanagisawa et al. in 1988, the presence of which has been identified in porcine, bovine and human [M. Yanagisawa et al., Nature, Vol. 332, 411 (1988)].
Endothelin includes 3 isopeptides named endothelin-1, endothelin-2 and endothelin-3, respectively. Of these isopeptides, endothelin-1 has been confirmed to show the highest activity in human body. Endothelin possesses strong and lasting action of constricting vascular smooth muscle cell and trachea, and induces hypertension and constriction of respiratory tract and, at a high concentration (i.e., about 1-about 50 pmol/ml in blood level), it can additionally induces ischemic cerebral and cardiac diseases such as cerebral apoplexy, stenocardia, myocardial infarction, cardiac incompetence and arrhythmia, nephropathy such as nephritis, circulatory failure of lung, liver and intestine, and asthma, thus in some cases killing animals.
Endothelin-1 is a 21-amino acid peptide which is produced by hydrolytically cleaving its precursor peptide, big endothelin-1 of the formula: ##STR1## with the endothelin converting enzyme at the bond between the tryptophane residue at the 21st position from the Nterminus and the valine residue at the 22nd position from the N-terminus (shown by the downward arrow). This hydrolysis process is considered to be essential for production of endothelin-1 in vivo. Reports on enzymes having the endothelin converting activity have been made on those in cultured bovine endothelial cells [K. Okada et al., Biochemical and Biophysical Research Communications, Vol. 171, No. 3, 1192 (1990)] and those in bovine adrenal medulla [T. Sawamura et al., Biochemical and Biophysical Research Communications, Vol. 168, No. 3, 1230 (1990)], but no reports have been made on enzymes of human origin having an endothelin converting activity.
Endothelin, which has remarkable physiological activities as described above, is produced enzymatically from its precursor, big endothelin and, therefore, serves to provide a means for inhibiting in vivo production of endothelin. In addition, this enzyme is expected to provide a useful reagent for analyzing the mechanism of vasoconstriction in vivo and for studying various diseases induced by endothelin.
Further, with elucidation of the endothelin converting enzyme, there can be provided an effective means for searching and developing an inhibitor of the enzyme, which is expected to be a means for prophylaxis and treatment of various diseases (hyperendothelinemia) induced by hypersecretion of endothelin, such as hypertension, constriction of trachea, ischemic brain diseases and heart diseases, nephropathy, circulation failure of various organs (e.g., lung, intestine, etc.), and asthma.
For the above-described reasons, there has been desired the elucidation of endothelin converting enzyme of human origin not having so far been found and a process for obtaining it.